To:  CTuckerNWIL

 

You read correctly, but that system was experimental and was used only on a forklift built especially for a material handling expo at Mccormick Place, Chicago in the late 1960s/early 1970s.  You might find some old publicity literature describing what was then called a "Gofor."   Also, for control details, look up U.S. Patent No. 3.512,072, Elevated Load Potential Energy Recovery, etc, etc. in Google Patents.  I am one of the two patent holders (my boss put his name first, of course).

 

To anyone reading this, I worked for A-C for 25 years in the industrial truck group and I am familiar with electric forklift technology.   I still maintain many industry contacts, so I'll try to answer any questions you might have or direct you to sources of parts or info.

 

 

 

If I suggest something you already know or have tried, just be patient and we'll find and resolve the problem.

 

First off, is the battery charged?  Do you have any dead cells?  Do the pump (lift) motor and power steering motors run OK?  If so, odds are the battery is OK.  If not, the battery may be the problem. 

 

Are the control and big high-power fuses OK?  They may look good, but you should run a resistance check to be sure.

 

Next, and VERY IMPORTANT,  safely block up the drive wheels so they cannot make contact with the floor or anything else if they rotate!!!!

 

Third, here's an old mechanic's trick--with the wheels blocked up, battery plugged in, use a piece of wood or non-conductive material, and carefully push the forward contactor solidly closed.  Holding it closed, then push the 1-A contactor solidly closed.  If the cabling and motor circuits (and the drive motor) are OK, the motor will jump to top speed in forward.  Do the same with the reverse contactor and 1-A.  If the motor runs in both directions, all the power circuits are OK.  If the motor runs in one direction only, then you know the other power circuit has a problem.  If the motor doesn't run at all, you may have a dead battery, open cabling connection, bad contactor tips, or badly worn motor brushes.

 

I don't know which contactors you have, but if the tips are worn out, replace them.  Don't file or sand them as they will have a tendency to arc or stick at a very inconvenient time.

 

Do the contactors pick up when you select a direction and step on the accelerator?  If not, then you may have a bad direction selector switch, or bad accelerator foot switch, or if so equipped, a bad brake pedal switch, or a bad seat cushion switch, or any of the connecting wires in those circuits.

 

Also, do you get any high pitched buzzing from the control when you try to drive the truck?  If so, that indicates an open freewheeling diode.

 

Give these ideas a try a try and let me know what you find out.  Please be safe and good hunting!!

 

NIKT

 

 

 

 

 

 Thanks for your reply. I had already checked all the items you mention before I contacted you the first time. You are very thorough! The Battery is fully charged 36 + volts and checked again under a load. No dead cells. Lift Motor runs and lift tilt and side shift all work. The Steering Pump motor runs, but the wheels do not turn left or right. I am assuming this to be a hydraulic unit using the same reservoir as the lift pump. Maybe I have a bad hyd cylinder or steering valve.

Contactors for reverse, forward, and the smaller  contactor that closes upon turning on the machine all actuate and have continuity.

I pulled all the drive motor wires off one at a time and cleaned the connections.

I had already blocked up the wheels to test and tried manually actuating the contacts although they worked fine with the accelerator.

 

I see we have at least two problems to solve--one, the drive system, and, two, the power steer system.

 

Let's keep chugging along here while my A-C pals keep digging for a wiring diagram.

 

Drive System:  Would you please clarify one more time--If you manually close both the Forward contactor and the 1-A bypas contactor, does the drive motor run?  And does the motor run with the Reverse contactor and the 1-A  both closed?  If the motor doesn't run under these conditions, then there is an open in the drive power circuit.   

 

You can check motor continuity:  With all cables disconnected from the motor, there should be continuity from S1  to  S2 (letters stamped into field ring).  These are the series field coils.  Note: some field terminals were  marked F1 and F2, so keep an eye open for this.  The armature terminals should be marked A1 and A2.  Both the armature and field windings in the motor should have a low resistance, typical HUNDRETHS of an ohm.  Usually the the fields almost never fail, but a shorted field coil(s) wold tend to make a running motor want to run faster, but pull an abnormally high current and while causing much brush sparking.  If there is no armature continuity, you may have stuck or worn brushes.  Remove the cover bands at the brush-end of the motor and take a look.  If the brushes seem to be well down into, or flush with the brushboxes, they are definitely worn out.  Brushes and all motor parts are readily available from people like Warfield Electric Co, 815-469-4094 for reasonable prices.

 

Power steer problem:  This sounds like a hydraulic problem.  If the lift and tilt work OK, then the odds are the fluid level is OK.  Since the power steer motor seems to run OK, then you may have a hose or component problem.  Check the hose that feeds the inlet port of the power steer pump to make sure it is not collapsing from suction vacuum.  It may help to know how this system works:  This system is a full power assisted sytem with no mechanical link between the steering wheel and the small diameter steerable wheels located at rear of the forklift.  The power steer pump sends fluid to an Orbitrol valve controlled by the steering wheel.  There are four ports in the steer valve--the inlet port gets pressurized fluid from the pump, while two of the ports are connected to the power steer cylinder.  When you turn the steering wheel to the left or right, fluid is directed to one side or the other of the power steer cylinder to move its piston one way or the other to steer left or right.  The fourth port on the Orbitrol is the drain line back to the reservoir.   I would suggest pulling the drain line that goes from the Orbitrol drain port to the tank, and aim it into a deep bucket.  Run the power steer motor briefly to see if fluid is being pumped at all.    Assuming there is sufficient fluid in the tank,  if there is no flow, then the suction hose may be collapsed or a filter may be clogged.  Usually a suction side restriction will result in pump cavitation and cause a high pitched noise.   If you have good flow in the drain line, turn the steering wheel to see if the steer cylinder and linkage move.  If not, try to raise the steer wheels off the ground and repeat the test.  If the wheels then steer, you may have an abnormally steering low relief pressure.  The relief valve is typically built into the power steer pump.  You should set relief pressure with a gauge as you could blow the lines with excess pressure.  You should hear the power steer motor/pump unit speed up and slow down as you steer , and you should hear the unit run slower when you get to either end of the stroke of the power steer cylinder.   If you get thes audible clues, but the no steering, you may have a rare case of the piston breaking loose from the piston rod and just moving back and forth in the cylinder without doing any steering.

 

Try these hints and let me know how you make out.

 

NIKT

 

 

Any suggestions would be appreciated.

BTW... the resevoir is full, the feed lines are not crushed, the battery is excellent, all other hydraulic functions work fine.

Thanks.

 

When I reinstalled the brushes, I didn't take note of the direction of the longer leads in the T and where they were, so I obviously installed them backwards and my motor spun backwards.  After correcting, the motor now spins the proper direction and power steering works excellent.

 

To note:  The proper direction for the pump on this machine is clockwise rotation when looking at the shaft of the pump (where it connects to the motor).  The fluid inlet is on the bottom, pressure outlet is on the top of the pump.

 

The reason I was not getting power steering to work after I initially installed the new brushes, then changed them and tested, was because when I went and changed them, I did so by not removing the entire motor from underneath the rear axle.  I just pulled off the back end of the motor housing where the brushes are, and switched them there.

 

PROBLEM WAS.... when I did so, I must have pulled on the armature slightly and it pulled away from the pump a little, dislodging the armature key.  So when I retested the motor with the brushes changed, the motor wasn't turning the pump and it was at that point that I thought I was going nuts.  I finally had enough and took it all out again, only to find the key sitting in the bottom of the motor housing and me feeling rather stupid.

 

In short, if your power steering needs servicing, elevate the rear of this model forklift (ON BLOCKS, safety first) and remove the entire unit because if my experience with the armature KEY is standard factory, then this is not like anything I've ever seen.  Most keys are insterted in the side of a shaft, but not this one.  It is a little round extension, male on one side, female slot on the other side, keyed into the end of the armature shaft and mates with the pump.  My pump still has an Allis Chalmers stamp on it, so I believe my entire setup is still factory.

 

At any rate, reading NIKT above shed some help about these forklifts for me, which was useful.  Hopefully my crazy experience will help someone else by reading this.

 

All the best.

Evidently, when you changed the brushes the first time, you did, as you correctly analyzed, inadvertantantly changed the armature connections causing reverse rotation.

 

 

 

 

I have lifted the drive wheels and tested. The drive works fine without load in both directions back and forth. There does not seem to be any hesitation with the drive wheels off the ground.

My first thoughts were the direction sensor or the drive potentiometer. After the wheels up test, I am not so sure about this.

Any comment?